The version of test-loader I have is 1.0.0. When i looked at the actual files, the index.js is quite bare. I don't know why the owner of this library tagged it as 1.0.0 as it does not do much... (well I suppose it is a "breaking change" technically speaking)

Anyway, I reverted my version to 0.1.3 and it seems to work now. Also i had to get rid of the test-loader portion in my vendorFiles option as i no longer needed it.